Frequency multiplication and displacement



Oct. 7, 1969 R. GERMANN ETAL FREQUENCY MULTIPLICATION AND DISPLACEMENTFiled March 29. 196'? 4 Sheets-Sheet i foi, www

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United States Patent O 3,471,763 FREQUENCY MULTIPLICATION ANDDISPLACEMENT Reimar Germann and Kurt Wiederwohl, Graz, Austria,

assignors, by mesne assignments, to Mobil Oil Corporation, New York,N.Y., a corporation of New York Filed Mar. 29, 1967, Ser. No. 626,755Claims priority, application Austria, Jan. 12, 1967, A 321/67 Int. Cl.H021) 5/34, 7/42 ABSTRACT F THE DISCLOSURE A method and means fordriving a synchronous motor characterized by novel circuitry formultiplying the frequency of a signal and displacing it by 90. Thefrequency multiplication system is characterized by the discharge of acapacitor to a constant current circuit for the production of a sawtoothvoltage which in turn actuates a Schmitt trigger. The leading andtrailing edges of the Schmitt trigger signal, upon differentiation andaddition, produce pulses having a frequency twice that of the initialsignal. The phase shifting circuit is characterized by doubling thefrequency of a first square wave signal to produce a second square wavesignal wherein the trailing edge actuates a bistable device to result ina 90 phase displaced square wave signal, in relation to the first squareWave signal.

Cross-reference This invention is suitable for use with the engineanalyzer synchronization system of copending application Ser. No.587,096, Oct. 17, 1966, Germann, Wiederwohl and Schwertfhrer, commonlyassigned. In said copending application the pressure patterns at thefuel injection lines to the cylinders of a diesel engine are displayedon an oscilloscope. The synchronization of such a system is provided Abyphotosensitive devices actuated by a motor driven by a signal from atransducer in one of the fuel injection lines. The motor is driven at arate proportional to the speed of the engine or of the fuel injectionpump.

The present invention is directed to an alternative system for drivingthe synchronous motor referred to in said copending application.

Summary of the invention The frequency multiplication method of thisinvention is characterized by the storage of initial pulses in anintegrating circuit, the discharge of these pulses to a constant currentcircuit for the formation of a sawtooth signal, the actuation of aSchmitt trigger by the sawtooth signal to provide a square wave,differentiation of the square wave to produce pulses representative ofits leading and trailing edge, and the addition of these pulses toprovide a signal which has a frequency twice that of the initial pulses.

The method of producing 90 phase displaced pulse is characterized by thegeneration of an initial square wave, the doubling of this initialsignal to produce a square wave having twice the initial frequency, thedifferentiation of the new square wave to produce a signallrepresentative of its trailing edge, and the use of this differentiatedsignal to actuate a bistable device to produce a square Wave pulse whichhas the same frequency as the initial pulse but is displaced by 90.

The above methods find use in the generation of signals for driving asynchronous motor at a speed controlled by the frequency of the initialpulses.

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Brief description of the drawings FIGURE 1 is a block diagram of thisinvention.

FIGURES 2-5 show portions of the circuitry used in this invention.

FIGURE 6 indicates the signal produced at the various points indicatedin FIGURE 1.

Description of specific embodiments In FIGURE l numerals 2 through 5refer to those ligures in which detailed embodiments of the circuitryare shown. The initial signal used in this invention is derived from atransducer 10 situated in the fuel injection line of a diesel engine(not shown). The signal from the transducer is transmitted by a sourcefollower amplifier 12 to a phase inverter 14 to provide a signalindicated by I. A trigger level adjuster 16 controls the amplitude towhich signal I must reach (see signal II) in order to actuate Schmitttrigger 18. The Schmitt trigger emits square wave pulses illustrated bysignal III. The Schmitt trigger actuates monostable vibrator 20 whichemits signal IV, which has sufficient duration to eliminate multipletriggering as indicated by the first pulses in signals II and III. Themonostable vibrator pulses are amplified and inverted in amplifier 22which emits pulses V. These signals from the amplifier areldifferentiated in means 24 to produce signal VI. The differentiatedsignal does not actually have the negative portion below the broken lineillustrated diagrammatically in VI, due to clipping device 26 whichremoves the negative excursion as indicated by signal VII. This effectis shown repeated below. The positive peaks of signal VII chargeintegrator 28, illustrated diagrammatically by signal VIII prior todischarge. The integrator is discharged to a constant current circuit 30to provide a sawtooth signal IX which is repositioned on the zero lineby DC decoupler 32 as indicated by signal X. This signal actuatesSchmitt trigger 34 to produce the controlled square Wave voltage XI. Thetrigger level adjuster ensures equal duration of the pulses of signalXI. In place of the Schmitt trigger, and those referred to below, anyother suitable level detector may be used, such as a conventionalvoltage comparator. Schmitt trigger signals XI are differentiated at 36to produce signal XII, which has its negative portion removed in clipper38 as indicated by signal XIII. These positive peaks, representative ofthe leading edge of Schmitt trigger signal XI are then transmitted tothe OR gate 40. Schmitt trigger signals XI are also transmitted to phaseinverter 42 to produce signal XIV which is differentiated in means 44 toproduce signal XV. Differentiated signal XV is clipped by .means 46, andthe positive peaks, signal XVI, representative of the trailing edge ofSchmitt trigger signal XI, are transmitted to OR gate 40. The OR gateproduces a series of positive peaks, signal XVII having twice thefrequency of the initial signal I. The signal XVII, Whi-ch may beamplified at this point, is then directed through integrator 48,discharge means 50, decoupler 52 and Schmitt trigger 54, whichcorrespond respectively with means 28, 30, 32 and 34. The modificationof signal XVII is indicated in its various stages by signals XVIIIthrough XXI. Schmitt trigger signal XXI has a frequency equal to twicethat of the previously produced Schmitt trigger signals, XI. Thetrailing edge of signal XXI triggers a bistable vibrator 56 to providesignal XXII. Signal XXII has the same frequency as signal XI, and itsphase is displaced by Signals XI and XXII, amplified at 62 and `60, maybe used to drive synchronous motor S8 in a manner similar to thatdescribed in copending application Ser. No. 587,096.

The electrical components described are conventional and may be found ina number of sources, such as the Transistor Manual, General ElectricCompany, 6th ed., Reference Data for Radio Engineers, InternationalTelephone and Telegraph, 4th ed., and other standard works. Anembodiment for several of these components is shown below, however, itwill be appreciated that numerous electrical designs could be derivedwithin the scope of the above disclosure.

FIGURES 2, 3, 4 and 5 present a more detailed embodiment of the systemof FIGURE 1. Like numbers in these figures refer to like components. Theletter R refers to resistors; the Values for the resistors and othercomponents can readily be chosen by one skilled in the art to match therequirements of this system.

FIGURE 2 shows the generation of signals VII, having the same frequencyas the initial pulses, I. FIGURE 3 depicts a system for the storage inan integration circuit of a series of signals and the production of asquare wave of controlled duration having the same frequency as saidstored signals. The system of FIGURE 3 is useful for generating thesignals shown in FIGURE 6 as VIII-XI and XVIII-XXI. FIGURE 4 depicts asystem for differentiating a square wave pulse to produce a signalhaving twice the frequency, signals XII-XVII. FIGURE 5 depicts a systemfor displacing a signal by 90 and using two square waves to drive asynchronous motor, signal XXII and signal XI.

In FIGURE 2 the signal from transducer 10 is directed to the base offield effect transistor 100. The output from transistor 100 is connectedthrough the indicated resistors and condenser 200 to transistor 102which serves as a phase inverter. As indicated the potential applied tothese transistors is +12 volts and -12 volts. Throughout these figures,arrows are used to indicate connections to power supply lines (notshown). The output of transistor 102 is connected through the indicateddiode 300 and condensers 202 and 204 to the trigger level adjustercomprising the indicated variable resistor 206. In place of elements102, 300 and 202, a simple Miller integrator circuit with appropriateemitter followers -could be used. The clipped signal from the triggerlevel adjuster actuates Schmitt trigger 18 which in turn is connected tomonostable vibrator 20. Each of the major elements which are not shownin detail, such as the Schmitt trigger and the monostable vibrator, isof conventional circuitry and is available as an on-the-shelf unit. Thesignal from the monostable vibrator 20 is connected to the base oftransistor 104 which acts as an amplifier and inverts the signal. Theinverted signal is directed to the base of transistor 106 which isarranged as an emitter follower. The signal from the emitter follower isdifferentiated by the circuit cornprising condenser 208 and the resistorwhich follows it. The negative portion of the differentiated signal isclipped [by means of diode 302.

As shown in FIGURE 3 the differentiated signal is passed to diode 304which is part of the integrator circuit comprising condenser 210. Thecharge stored on condenser 210 is discharged at a controlled rate bymeans of transistor 108 arranged in a constant current circuit. Thesawtooth signal which is generated passes through transistors 110, 112,and 114 which serve the function of maintaining the form of the signalby matching the impedance in the circuit and by passing the signalthrough an emitter follower. The sawtooth signal is then decoupled ofits DC component in condenser 212 from which it passes to the triggerlevel adjuster including variable resistor 214. The signal then passesthrough emitter follower 116 which is used to actuate a Schmitt trigger34. As indicated in FIGURE 1, this circuit is duplicated to provideanother means for producing a square wave signal -(referred to below).

In FIGURE 4 the signal from Schmitt trigger 314, of FIGURE 3, isdifferentiated by means of condenser 216 and the resistor which followsit. The negative portion of the differentiated signal is clipped bymeans of diode 306. In a parallel circuit the Schmitt trigger signalfrom 34 is passed to transistor 11S which acts as a phase inverter. Theinverter signal is differentiated by means of condenser 218 and theresistor which follows it. The negative portion of the differentiatedsignal is clipped by means of diode 308. The positive peaks of thedifferentiated signals from condensers 216 and 218 are passed inparallel to an OR gate comprising diodes 310 and 312. These positivesignals are in effect added through the OR gate and appear as acomposite signal XVII having twice the frequency of XIII or XVI.

Signal XVII passes through lter condenser 219 to a circuit which is aduplicate of that shown in FIGURE 3. In this duplicate the Schmitttrigger is referred to as 54, as in FIGURE 1. The signal from 54 is usedto actuate a bistable vibrator 56. In a suitable bistable vibrator, forexample, that shown in Transistor Circuit Design, by Texas Instruments,Inc. (McGraw-Hill Book Company, 1963), the square wave XXI would bedifferentiated and the positive portion clipped to provide a square waveoutput, XXII, which is shaped by the trailing edges of signal XXI. Thesignal from bistable vibrator 56 and the signal from Schmitt trigger 34(respectively signals XXII and XI) are passed to amplifiers 60 and 62and then to synchronous motor 58. The speed of the synchronous motor isthusly controlled by the frequency of the initial signal I.

This invention has been described in terms of specific embodiments setforth in detail, but it should be understood that these are by way ofillustration only and that the invention is not necessarily limitedthereto. Alternative constructions will become apparent to those skilledin the art in view of this disclosure, and accordingly modifications ofthe apparatus and process disclosed herein are to be contemplated withinthe spirit of this invention and the following claims.

What is claimed is:

1. Means for driving a synchronous motor at a speed responsive to thefrequency of a first series of pulses, which comprises:

(a) means to store a charge representative of each of said pulses,

(b) operatively connected therewith constant current discharge means toproduce a sawtooth signal,

(c) a Schmitt trigger device actuated by a voltage approximately midwaybetween the peak and valley of said sawtooth signal, to produce a firstsquare wave voltage,

(d) means to generate a second square wave voltage of twice thefrequency and half the pulse duration of said first square wave voltage,and

(e) means to generate a third square wave voltage which has its leadingand trailing edges defined by the trailing edges of said second squarewave voltage, wherein said synchronous motor is driven by said first andthird square wave voltages.

2. The system of claim 1 wherein said means (d) to generate a secondsquare wave voltage includes:

(f) means to provide as an output a second series of pulsesrepresentative of the leading and trailing edges of said first squarewave voltage,

(g) second means to store a charge representative of each of said secondseries of pulses,

(h) operatively connected therewith second constant current dischargemeans to produce a second sawtooth signal, and

(i) a second Schmitt trigger device actuated by a voltage approximatelymidway between the peak and valley of said second sawtooth signal, toproduce said second square wave voltage.

3. The system of claim 2 wherein said means (f) to prove as an output asecond series of pulses includes:

(j) means to differentiate said first square wave voltage,

(k) operatively connected therewith means to provide two series ofpulses of the same polarity, one of 3,471,763 5 `6 which isrepresentative of the positive peaks and the 3,264,541 8/ 1966 Mell318--171 other representative of the negative peaks from said 3,356,92112/ 1967 Bradford et al. 318-341 XR means to diierentiate and (i) an ORgate responsive to said two series of pulses. CRIS L RADER, PrimaryEXamrler EN R B N References Cited 5 G E U I SON, Ass1stant ExammerUNITED STATES PATENTS 1 U.s. C1. XR. 2,863,108 12/1958 Raifensperger31a- 171 3 8441

